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hesitating under boost

u63af

u63af

Member
My car started hesitating under boost the other day. The boost starts coming in and then about 4,000 rpm the car seems to hesitate a bit and then pull again. I have changed the plugs, rotor arm and cap and this has made no difference. Anyone got any ideas?

cheers
sandy
 
Do you have a boost gauge too see what the boost is doing, it could be the boost dropping which might indicate trouble with the turbo/wastegate etc or could be the injection system playing up and the fuelling is all out of sorts.
 
How old are the leads, rotor arm and dizzy? I found with mine they were probably very old - they were certainly way past their best and even though I hadn't started having problems.
 
I have a boost gauge. I fitted the car with a tial dpw, greddy ebc, promax chips and 3 bar fpr, These were fitted 3 months ago, car has been perfect after that until last week. Leads are 3 months old (magnecore), had new cap and arm at the weekend. Cant figure it out. It boosts in well and then hesitates for a second and then pulls again. It will boost to 12 psi with ebc off and 16 psi with it on. I was thinking it may be fueling so will change the fuel filter.

Any ideas if the fuel filter doesnt sort it?

Cheers
 
Hi,

I had the same problem with my 951 several years ago. Change the fuel pump and the filter and get a fuel pressure gauge for the end of the fuel rail to check that with the vacuum hose pulled from the FPR you're getting 3bar +
 
I was worried about the pump as one of my mates had a probem with one of his turbo cars like this and it was the fuel pump. What sort of pump should I get? Is the standard one ok or should I get an aftermarket one?

Cheers
Sandy
 
A lot of chipsets which use some of the standard software are prone to problems exactly at 4000 rpm.

Often they will be ok, until something goes out of spec, then at 4000 rpm the software falls on its face for a moment. We used to see this often when we used to use Guru chips years ago.

Check the distributor cap, rotor arm, plugs, plug leads... also check for cracks in rubber hoses, even the non boosted ones such as the j-hose from the turbo to the airflow meter.
 
Jon,
Thanks for the help. I already replaced the plugs, rotor arm, cap and leads. Will try taking off boost hoses, cleaning throttle position sensor, idle stabilizer, re-gapping plugs and changin fuel filte (as it is due anyway).

Would there just be a problem with the chips due to a problem elsewhere and they cannot compensate for it? (i.e if it is taking in unmetered air due to leak etc.) Or do you think that the chips may be faulty?

Cheers
Sandy
 
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